[java] What's the difference between compiled and interpreted language?

After reading some material on this subject I'm still not sure what the difference between a compiled language and an interpreted language is. I was told this is one of the differences between Java and JavaScript. Would someone please help me in understanding it?

Here is the Basic Difference between Compiler vs Interpreter Language.

Compiler Language

• Takes entire program as single input and converts it into object code which is stored in the file.
• Intermediate Object code is generated
• e.g: C,C++
• Compiled programs run faster because compilation is done before execution.
• Memory requirement is more due to the creation of object code.
• Error are displayed after the entire program is compiled
• Source code ---Compiler ---Machine Code ---Output

Interpreter Language:

• Takes single instruction as single input and executes instructions.
• Intermediate Object code is NOT generated
• e.g: Perl, Python, Matlab
• Interpreted programs run slower because compilation and execution take place simultaneously.
• Memory requirement is less.
• Error are displayed for every single instruction.
• Source Code ---Interpreter ---Output

Java and JavaScript are a fairly bad example to demonstrate this difference_{, because both are interpreted languages}. Java _{(interpreted)} and C (or C++) _(compiled) might have been a better example.

_{Why the striked-through text? As this answer correctly points out, interpreted/compiled is about a concrete implementation of a language, not about the language per se. While statements like "C is a compiled language" are generally true, there's nothing to stop someone from writing a C language interpreter. In fact, interpreters for C do exist.}

Basically, compiled code can be executed directly by the computer's CPU. That is, the executable code is specified in the CPU's "native" language (assembly language).

The code of interpreted languages however must be translated at run-time from any format to CPU machine instructions. This translation is done by an interpreter.

Another way of putting it is that interpreted _{languages are} code is translated to machine instructions step-by-step while the program is being executed, while compiled _{languages have} code has been translated before program execution.

As other have said, compiled and interpreted are specific to an implementation of a programming language; they are not inherent in the language. For example, there are C interpreters.

However, we can (and in practice we do) classify programming languages based on its most common (sometimes canonical) implementation. For example, we say C is compiled.

First, we must define without ambiguity interpreters and compilers:

An interpreter for language X is a program (or a machine, or just some kind of mechanism in general) that executes any program p written in language X such that it performs the effects and evaluates the results as prescribed by the specification of X.

A compiler from X to Y is a program (or a machine, or just some kind of mechanism in general) that translates any program p from some language X into a semantically equivalent program p' in some language Y in such a way that interpreting p' with an interpreter for Y will yield the same results and have the same effects as interpreting p with an interpreter for X.

Notice that from a programmer point of view, CPUs are machine interpreters for their respective native machine language.

Now, we can do a tentative classification of programming languages into 3 categories depending on its most common implementation:

• Hard Compiled languages: When the programs are compiled entirely to machine language. The only interpreter used is a CPU. Example: Usually, to run a program in C, the source code is compiled to machine language, which is then executed by a CPU.
• Interpreted languages: When there is no compilation of any part of the original program to machine language. In other words, no new machine code is generated; only existing machine code is executed. An interpreter other than the CPU must also be used (usually a program).Example: In the canonical implementation of Python, the source code is compiled first to Python bytecode and then that bytecode is executed by CPython, an interpreter program for Python bytecode.
• Soft Compiled languages: When an interpreter other than the CPU is used but also parts of the original program may be compiled to machine language. This is the case of Java, where the source code is compiled to bytecode first and then, the bytecode may be interpreted by the Java Interpreter and/or further compiled by the JIT compiler.

Sometimes, soft and hard compiled languages are refered to simply compiled, thus C#, Java, C, C++ are said to be compiled.

Within this categorization, JavaScript used to be an interpreted language, but that was many years ago. Nowadays, it is JIT-compiled to native machine language in most major JavaScript implementations so I would say that it falls into soft compiled languages.

A compiler, in general, reads higher level language computer code and converts it to either p-code or native machine code. An interpreter runs directly from p-code or an interpreted code such as Basic or Lisp. Typically, compiled code runs much faster, is more compact, and has already found all of the syntax errors and many of the illegal reference errors. Interpreted code only finds such errors after the application attempts to interpret the affected code. Interpreted code is often good for simple applications that will only be used once or at most a couple times, or maybe even for prototyping. Compiled code is better for serious applications. A compiler first takes in the entire program, checks for errors, compiles it and then executes it. Whereas, an interpreter does this line by line, so it takes one line, checks it for errors, and then executes it.

If you need more information, just Google for "difference between compiler and interpreter".

Interpreted language is executed at the run time according to the instructions like in shell scripting and compiled language is one which is compiled (changed into Assembly language, which CPU can understand ) and then executed like in c++.

It is a very murky distinction, and in fact generally not a property of a language itself, but rather of the program you are using to execute code in that language.

However, most languages are used primarily in one form or the other, and yes, Java is essentially always compiled, while javascript is essentially always interpreted.

To compile source code is to run a program on it that generates a binary, executable file that, when run, has the behavior defined by the source. For instance, javac compiles human-readbale .java files into machine-readable .class files.

To interpret source code is run a program on it that produces the defined behavior right away, without generating an intermediary file. For instance, when your web browser loads stackoverflow.com, it interprets a bunch of javascript (which you can look at by viewing the page source) and produces lots of the nice effects these pages have - for instance, upvoting, or the little notifier bars across the top.